"My 'terrorist' status derives from opinions of mine posted in this site with respect to what I consider to be the solution to deal with criminals such as Hugo Chávez, ie violence," explained Aleksander Boyd, the de facto London-based representative of the Venezuelan opposition in Britain.

You can get a flavour of the sort of violence Boyd has in mind from reading his website. In March 2004, he wrote: "I wish I was Genghis Khan, I wish I had eaten my half-brother ... Therefore the scum of this earth aka Hugo Chávez and followers would not be willing to piss me off. Ergo they would be extremely careful of not treading on my rights. Attempts to conquer commanded by me would encounter nothing less than total submission owing to the sheer fear that my presence would cause."

Boyd continued in similar vein: "I wish I was the Khan an order my hordes to capture them and pour melted silver into their eyes ... I wish I could decapitate in public plazas Lina Ron and Diosdado Cabello [two Venezuelan politicians]. I wish I could torture for the rest of his remaining existence Vice President Jose Vicente Rangel ... I wish I could fly over Caracas slums throwing the dead bodies of the criminals that have destroyed my country ... Only barbaric practices will neutralize them, much the same way the Khan did. I wish I was him."

This was no isolated outburst. For the past four years, Boyd has been consistently promoting terrorism against the democratically elected government of Venezuela and its supporters. In March 2005, he declared: "Re: advocating for violence yes I have mentioned in many occasions that in my view that is the only solution left for dealing with Chávez."

Boyd does not shy away from naming those he describes as "the scum of this earth". In August 2005, he published a list of serving army officers under the heading "Venezuelan traitors", together with the ominous words: "We shall see that these men pay."

You can therefore imagine my surprise when I discovered that the leader of the Conservative group on the Greater London Assembly, Angie Bray, had arranged to meet with a group including Boyd and has since been describing them as persecuted dissidents who "have had to flee abroad".

In fact, far from being a political refugee, Boyd regularly travels unhindered to and from London and Caracas to drum up support for his extremist views.

The Conservative party's meeting with the opposition group took place in May last year, when President Hugo Chávez came to London to address the GLA as a guest of Mayor Ken Livingstone. The Conservative group boycotted the meeting, and instead invited the "dissidents" to brief them about what Bray describes as Venezuela's descent into "tyranny".

"Of course, Ken banned them from the building" and the meeting had to be reconvened "in an office across the road", wrote Angie Bray last week in her Cif blog.

Angie Bray had two purposes in mind when she wrote her article. The first was to smear Chávez as a tyrant, and the second was to boost Tory candidate Boris Johnson's chances of becoming mayor by smearing Livingstone as "a staunch ally of a tyrant". Bray claims that the "dissidents" showed her proof that secret ballots are "unheard of in Chávez's Venezuela" and that if you don't vote for Chávez "you don't get access to vital poverty relief schemes".

Bray's allegations, however, are contradicted by international election observers. Venezuela's elections have repeatedly been declared free and fair by the Carter Center, the Organisation of American States and the European Union. The last report from the EU Election Observation Mission states that the 2006 Presidential Elections "were held in respect of national laws and international standards concerning electoral administration and the electronic voting system".

The EU report goes on to confirm "that the fingerprint reading devices (captahuellas) neither violate the secrecy of the vote, nor are a source of fraud". And contrary to what Bray claims, the electoral register does not record how citizens voted: "The voter lists include the voter's name, ID number, and three blank spaces to add whether the voter turned up to vote (voted/did not turn up), the voter's fingerprint, and signature."

Angie Bray may have been misled about Venezuela's electoral process, but she cannot plead ignorance about Boyd's advocacy of violence against the Venezuelan government and its supporters. Ken Livingstone has spelt out in clear and detailed terms his reasons for banning Boyd from City Hall, both in press releases and during Mayor's Question Time. In May last year, Livingstone told assembly members that a man who talks about "pouring molten silver into the eye sockets of his opponents, is not someone you could seriously expect us to allow into this building".

This raises some awkward questions for David Cameron. Is he aware that the leadership of his London party is consorting with a man who wishes he had eaten his half-brother and dreams of torturing and murdering people?

More importantly, now that he does know, what is he going to do about it?